Recent Developments in Optical Detection Technologies in Lab-on-a-Chip Devices for Biosensing Applications

The field of microfluidics has yet to develop practical devices that provide real clinical value. One of the main reasons for this is the difficulty in realizing low-cost, sensitive, reproducible, and portable analyte detection microfluidic systems. Previous research has addressed two main approaches for the detection technologies in lab-on-a-chip devices: (a) study of the compatibility of conventional instrumentation with microfluidic structures, and (b) integration of innovative sensors contained within the microfluidic system. Despite the recent advances in electrochemical and mechanical based sensors, their drawbacks pose important challenges to their application in disposable microfluidic devices. Instead, optical detection remains an attractive solution for lab-on-a-chip devices, because of the ubiquity of the optical methods in the laboratory. Besides, robust and cost-effective devices for use in the field can be realized by integrating proper optical detection technologies on chips. This review examines the recent developments in detection technologies applied to microfluidic biosensors, especially addressing several optical methods, including fluorescence, chemiluminescence, absorbance and surface plasmon resonance

Microstructure and Photoelectric Response of Gold Nanocrystalline on TiO₂ Nanotube Arrays

In this paper, we report photoelectrical response of gold nanocrystalline on TiO₂ nanotubes (TNTs) with Au morphology ranging from nanoparticles, thin nanoring to thick nanoring. The gold nanocrystallines are loaded on the TNT by the facile magnetron sputtering technique. Compared with pristine TNT, the gold-decorated TNTs have shown obvious light absorption at wavelength of 380–850 nm as well as dependence of surface plasmonic resonance (SPR) on Au morphology. Photocurrent response under white light illumination presents around 4 times enhancement on all gold-decorated nanotubes at an applied voltage of 0.2 V. Transient current measurement reveals different ramping up behavior on nanoparticles and nanoring-coated TNTs at the onset of illumination. Full-field electromagnetic wave simulation based on finite element analysis (FEA) indicates that the shifting of SPR peaks is a joint effect of the size/aspect ratio, morphology, and amount of the nanocrystalline Au. Meanwhile, the FEA indicates that instant current response upon illumination on gold nanoparticles and nanoring structures are dependent on the electric field distribution, the behavior of charge carriers along longitudinal dimension of the TNT arrays. This study provides a perspective on SPR effect related to the enhanced photocurrent response on TNT arrays

Local Synthesis of Carbon Nanotubes in Silicon Microsystems: The Effect of Temperature Distribution on Growth Structure

Local synthesis and direct integration of carbon nanotubes (CNTs) into microsystems is a promising method for producing CNT-based devices in a single step, low-cost, and wafer-level, CMOS/MEMS-compatible process. In this report, the structure of the locally grown CNTs are studied by transmission imaging in scanning electron microscopy—S(T)EM. The characterization is performed directly on the microsystem, without any post-synthesis processing required. The results show an effect of temperature on the structure of CNTs: high temperature favors thin and regular structures, whereas low temperature favors “bamboo-like” structures

Integration of Carbon Nanotubes in Microsystems: Local Growth and Electrical Properties of Contacts

Carbon nanotubes (CNTs) have been directly grown onto a silicon microsystem by a local synthesis method. This method has potential for wafer-level complimentary metal-oxide-semiconductor (CMOS) transistor-compatible integration of CNTs into more complex Si microsystems; enabling, e.g., gas sensors at low cost. In this work, we demonstrate that the characteristics of CNTs grown on specific locations can be changed by tuning the synthesis conditions. We also investigate the role of the contact between CNTs and the Si microsystem; observing a large influence on the electrical characteristics of our devices. Different contact modes can render either an ohmic or Schottky-like rectifying characteristics

Integration of Carbon Nanotubes in Microsystems: Local Growth and Electrical Properties of Contacts

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Study of electrical field distribution and growth of gradient-arrayed TiO2 nanotubes by electrochemical anodization

Conference Name:2013 13th IEEE International Conference on Nanotechnology, IEEE-NANO 2013. Conference Address: Beijing, China. Time:August 5, 2013 - August 8, 2013.IEEE Nanotechnology Council (NTC); China Association for Science and Technology; The Chinese Academy of Sciences (CAS); The Chinese Academy of Engineering (CAE); Chinese Society of Micro-Nano Technology (CSMNT)In this paper, we report the simulation of electrical field distribution and growth of gradient arrayed TiO2 nanotubes by electrochemical anodization. A rectangle electrochemical electrode configuration, in which the end of cathode (Pt wire) is perpendicularly pointed to anode surface (Ti foil), is applied in NH4F glycol electrolyte. Electric field distribution on the surface of the titanium foil shows exponentially decreasing behavior as increasing the distance from the end of cathode. The relationship between nanotube diameter and applied voltage has been analyzed according to the images of Scanning Electron Microscopy (SEM) and simulated electrical distribution. These gradient TiO2 nanotube arrays might be a promising nano-architecture for increasing photon-to-electrical conversion efficiency of dye sensitized solar cells (DSSC). ? 2013 IEEE